1. Field of the Invention
The present invention relates to an automatic gang switch having a heat ray sensor for detecting heat rays emitted from a human body to turn a load on or off.
2. Description of the Related Art
In some of automatic gang switches having a heat ray sensor, heat rays emitted from the human body are collected on a human body detecting sensor such, for example, as a pyroelectric sensor via a lens in a predetermined detection region, and a load (for example, a light fixture) is on-off controlled based on a human body detecting signal from the human body detecting sensor. In general, such automatic gang switches are flush-mounted on a wall surface (building or working surface) of a front door, a corridor or the like, using a mounting frame fixed to the wall surface, to automatically turn on or off a lighting load by detecting a person passing through the front door, the corridor or the like.
In the automatic gang switches of the above-described construction, however, a switch for changing over the operation mode or performing various setting is accommodated within the body and, hence, cannot be operated from the front side, making it difficult to perform such setting.
The present invention has been developed to overcome the above-described disadvantages.
It is accordingly an objective of the present invention to provide an improved automatic gang switch having a heat ray sensor which is capable of easily performing a setting operation.
In accomplishing the above and other objectives, the automatic gang switch having a heat ray sensor according to the present invention is fixedly mounted on a mounting frame that has a generally rectangular opening defined therein and is secured to a substantially vertical wall. The automatic gang switch includes a housing having a body and a cover and also having a generally rectangular front portion and a mounting means for mounting the housing on the mounting frame, wherein the length of the housing is approximately two thirds of that of the generally rectangular opening of the mounting frame and the width of the housing is approximately equal to that of the generally rectangular opening of the mounting frame. The automatic gang switch also includes a human body detecting section accommodated in the housing for detecting heat rays emitted from a human body and a circuit section accommodated in the housing. The circuit section includes a control circuit for generating a control signal to turn a load on for a predetermined operation holding time when the human body detecting section generates a detection signal, a load control circuit connected to a power source and the load in series via two connecting terminals for turning on or off power supply to the load depending on the control signal, an off-time power circuit connected in parallel with the load control circuit and having an input impedance with which the load is not driven when the load control circuit is off, the off-time power circuit supplying an electric power to the control circuit when the load control circuit is off, and an on-time power circuit for supplying the electric power to the control circuit when the load control circuit is on. The automatic gang switch further includes a time setting section for setting an operation holding time and a mode setting section for changing over an operation mode of the control circuit to one of an automatic mode in which the load is automatically turned on or off depending on the detection signal from the human body detecting section, a continuous ON mode in which the load is kept on irrespective of the detection signal, and a continuous OFF mode in which the load is kept off irrespective of the detection signal. The human body detecting section, the time setting section, and the mode setting section are disposed on the front portion of the housing which is exposed from the generally rectangular opening of the mounting frame.
By the above-described construction, the automatic gang switch is fixed to a wall surface (building surface) via a ready-made mounting frame using the mounting means formed with the housing. Furthermore, because the length of the housing is approximately two thirds of that of a generally rectangular opening formed in the ready-made mounting frame and the width of the housing is approximately equal to that of the generally rectangular opening, the automatic gang switch can be juxtaposed with a flush-type wiring device of a size of single module.
It is to be noted here that some of the ready-made mounting frames for large rectangular ganged wiring devices standardized by JIS (Japanese Industrial Standard) have a generally rectangular opening that has a length approximately equal to the size of triple modules and a width approximately equal to the size of single module (the size of single module is a unit size of such large rectangular ganged wiring devices).
Also, because the human body detecting section, the time setting section, and the mode setting section are located on the front portion of the housing exposed from the opening of the mounting frame, the operation holding time or the operation mode can be set from the front face side, thus facilitating the setting operations. In addition, the electrical connection of a series circuit of the power source and the load between the two connecting terminals can reduce the number of connecting terminals, compared with the case where the connecting terminals to which the power source is connected and those to which the load is connected are separately provided. As a result, the space for accommodating the connecting terminals can be reduced, making it possible to reduce the housing.
Advantageously, the time setting section, the mode setting section, and the human body detecting section are positioned in this order from above.
The automatic gang switch further includes a lens mounted on the front portion of the housing for collecting the heat rays from a predetermined detection region on the human body detecting section, and a detection region limiting cover slidably mounted on the front portion of the housing for limiting the detection region. The detecting region limiting cover acts to block heat rays from an unnecessary region, thereby preventing malfunction of the human body detecting section. Also, because the detection region limiting cover is slidably mounted on the housing, the region to be shielded can be easily changed.
The automatic gang switch further includes first and second cover support members each having an arcuated cross-section, wherein the detection region limiting cover has an arcuated cross-section and is interposed between the first and second cover support members, and wherein the detection region limiting cover has a radius different from a radius of inner peripheral faces of the first cover support members and from a radius of outer peripheral faces of the second cover support members.
By the above-described construction, the difference in radius applies forces from the first and second cover support members to the detection region limiting cover and enlarges the contact resistance between the detection region limiting cover and the first and second cover support members. Accordingly, even if the detection region limiting cover is touched in error or vibration occurs, the detection region limiting cover does not easily move, thus preventing a change in the position thereof after adjustment. Also, because the detection region limiting cover is placed between the first and second cover support members in a bent or deformed state, a slippage during assembling or a variation in the size of component parts can be absorbed.
Preferably, the detection region limiting cover is disposed above the lens with a clearance therebetween. If the detection region limiting cover is held in close contact with the lens surface, the detection region limiting cover blocks all heat rays incident on the lens surface from a plurality of directions. However, the provision of the clearance between the detection region limiting cover and the lens makes it possible to selectively block the heat rays incident on the lens surface from the plurality of directions.
The detection area limiting cover may have projections formed therewith, while at least one of the first and second cover support members may have grooves defined therein for engagement with the projections. Such engagement generates a feeling of click and facilitates adjustment of the position.
The first cover support members may have a stopper formed therewith for maintaining at least a part of the detection region. The stopper acts to prevent the detection region limiting cover from being closed by mischief and, hence, a complete shading is avoided.
The detection region limiting cover may be made up of a plurality of plates. This construction can reduce the size of individual plates, compared with the case where the detection region limiting cover is made up of a single plate. Accordingly, the space for accommodating the detection region limiting cover can be reduced, resulting in a reduction in size of the housing.
Alternatively, the detection region limiting cover may have a flexible portion that expands or contracts according to the position of the detection region limiting cover. This construction can also reduce the space for accommodating the detection region limiting cover, resulting in a reduction in size of the housing.
Conveniently, the lens has a lens cover integrally formed therewith for covering a front face thereof. The lens cover acts to enhance the appearance of the automatic gang switch, and the one-piece construction of the lens with the lens cover can reduce the number of component parts.
Advantageously, the automatic gang switch further includes a door pivotally mounted on the front portion of the housing. The door prevents the setting of the time setting portion from being changed, for example, by mischief.
The door has opposite side walls having respective shafts formed therewith, and the housing has a bearing member for supporting the shafts. In this case, the shafts have an increasing diameter toward the side walls. The increasing diameter causes the shafts to be resistant to being broken.
Conveniently, the distance between edges of the side walls and centers of the shafts is greater than the distance between the centers of the shafts and the surface of the front portion of the housing on which the door is mounted. By so doing, when the door is opened or closed, the edges of the side walls are brought into contact with the surface of the housing. As a result, the side walls are pushed and bent outwardly, and a force for opening or closing the door acts on the side walls, thus preventing an unexpected closing of the door during setting and preventing an unexpected opening of the door from a closed state.
Again conveniently, the time setting section changes the operation holding time logarithmically depending on a change over operation thereof. By this construction, the set interval of the operation holding time is made smaller on the short time side than on the long time side. Accordingly, even if the adjustable range of the operation holding time is relatively wide, the time setting can be easily performed using only one time setting section.
It may be so designed that the operation mode of the control circuit can be set to one of the continuous ON mode and the continuous Off mode by the change over operation of the time setting section. By so doing, the time setting section can also be used as a mode setting section, resulting in a reduction in the number of component parts.
The automatic gang switch further includes a radiation plate accommodated in the housing and a circuit element thermally coupled to the radiation plate, wherein the housing has a plurality of communication holes defined therein, and the radiation plate has a plurality of through holes defined therein at portions other than those confronting the communication holes.
By the above-described construction, because the open air flows in and out of the housing through the communication holes thereof and the through holes of the radiation plate, the heat radiating effect can be enhanced. Also, because the inside of the housing is shielded by the radiation plate, the appearance of the automatic gang switch can be enhanced.
It is preferred that the load control circuit includes a triac connected between the two connecting terminals.
Alternatively, the load control circuit includes a relay having a relay contact connected between the two connecting terminals. The provision of such a relay in place of the triac can reduce heat generated by the load control circuit.
Again alternatively, the load control circuit includes a triac connected between the two connecting terminals and a relay having a relay contact connected in parallel with the triac, wherein the control circuit turns on the relay contact at a start of power supply to the load under a condition in which the triac is on.
By this construction, at the start of power supply to the load, the triac is first turned on and, hence, no rush current flows through the relay contact. Also, a relatively small relay can be used for a load having a large rush current. Further, compared with the case where only the triac is used, the current flowing through the triac is reduced, resulting in a reduction in heat generation.